Add rules to install generated headers

Originally committed as revision 21320 to svn://svn.ffmpeg.org/ffmpeg/trunk

Makefile

@@ -49,7 +49,7 @@ $(PROGS): %$(EXESUF): %_g$(EXESUF)
 
 SUBDIR_VARS := OBJS FFLIBS CLEANFILES DIRS TESTPROGS EXAMPLES SKIPHEADERS \
                ALTIVEC-OBJS MMX-OBJS NEON-OBJS X86-OBJS YASM-OBJS-FFT YASM-OBJS \
-               HOSTPROGS
+               HOSTPROGS BUILT_HEADERS
 
 define RESET
 $(1) :=

subdir.mak

@@ -80,6 +80,9 @@ install-headers::
 	install -d "$(INCINSTDIR)"
 	install -d "$(LIBDIR)/pkgconfig"
 	install -m 644 $(addprefix "$(SRC_DIR)"/,$(HEADERS)) "$(INCINSTDIR)"
+ifdef BUILT_HEADERS
+	install -m 644 $(addprefix $(SUBDIR),$(BUILT_HEADERS)) "$(INCINSTDIR)"
+endif
 	install -m 644 $(BUILD_ROOT)/lib$(NAME)/lib$(NAME).pc "$(LIBDIR)/pkgconfig"
 endef